How functional is functional? Ecological groupings in terrestrial animal ecology: towards an animal functional type approach

Abstract

Understanding mechanisms to predict changes in plant and animal communities is a key challenge in ecology. The need to transfer knowledge gained from single species to a more generalized approach has led to the development of categorization systems where species' similarities in life strategies and traits are classified into ecological groups (EGs) like functional groups/types or guilds. While approaches in plant ecology undergo a steady improvement and refinement of methodologies, progression in animal ecology is lagging behind. With this review, we aim to initiate a further development of functional classification systems in animal ecology, comparable to recent developments in plant ecology. We here (i) give an overview of terms and definitions of EGs in animal ecology, (ii) discuss existing classification systems, methods and application areas of EGs (focusing on terrestrial vertebrates), and (iii) provide a ''roadmap towards an animal functional type approach'' for improving the application of EGs and classifications in animal ecology. We found that an animal functional type approach requires: (i) the identification of core traits describing species' dependency on their habitat and life history traits, (ii) an optimization of trait selection by clustering traits into hierarchies, (iii) the assessment of ''soft traits'' as substitute for hardly measurable traits, e.g. body size for dispersal ability, and (iv) testing of delineated groups for validation including experiments.

The role of eco-evolutionary experience in invasion success

“…functional groups or types) can be used instead of guilds as well (for more details on ecological groupings, see e.g. Hawkins and MacMahon 1989, Wilson 1999, Blondel 2003, Blaum et al 2011). …”

Going Back to Basics: Importance of Ecophysiology when Choosing Functional Traits for Studying Communities and Ecosystems

“…Although the functional approach has been developed mostly under the scope of plant ecology, recent studies have successfully used functional traits to explain response of animal communities to environmental factors (Blaum et al 2011;Dias et al 2013b). However, as there is still no consensus among animal ecologists on what the most important traits are and what is the best way to measure them, establishing criteria for choosing and validating adequate traits is especially important in the scope of animal ecology.…”

Variation in hierarchical guild structure between two bird assemblages of a wetland in the Mexican Pacific

“…In these circumstances, alternative methods of classifying species allow researchers to evaluate patterns of resource use among co-occurring species. If more information becomes available, then applying multivariate analyses could provide an interesting opportunity for comparisons between methods (Wiens, 1989;Blaum et al, 2011).…”

“…Although a guild can be broadly defined as any group of species that are similar in an ecologically relevant way (Wilson, 1999), the original concept was specifically developed in the context of competition between bird species (Root, 1967) and that research agenda is on-going (e.g., Rodríguez, Jansson, & Andrén, 2007). Alternatively, guild members are perceived to converge on abundant resources (Jaksić, 1981;Hubbell, 2005) and this view enables comparisons between assemblages and the analysis of how resources or habitat variables shape assemblage structure (Mac Nally, 1994;Blaum, Mosner, Schwager, & Jeltsch, 2011;González-Salazar, Martínez-Meyer, & López-Santiago, 2014). Because they are taxonomically circumscribed, bird guilds are a class of assemblage guild (Jaksić, 1981), which is synonymous with ensemble (Fauth et al, 1996).…”